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1、UnitTwoDieDesign模具与数控专业英语2.5BendingDieDesign模具与数控专业英语Bendingisofthemostcommonformingoperations.Wemerelyhavetolookatthecomponentsinanautomobileoranappliance—oratapapercliporafilecabinet—toappreciatehowmanypartsareshapedbybending.Bendingisusednotonlytoformflanges,seams,andcorrugationsbutalsotoimpartstiffnesstothepart(byincreasingitsmomentofinertia).模具与数控专业英语TheterminologyusedinbendingisshowninFigure2-12.Notethat,Inbending,theouterfibersofthematerialareintension,whiletheinnerfibersareincompression。
2、.BecauseofthePoisson’sratio,thewidthofthepart(bendlength,L)intheouterregionissmaller,andintheinnerregionitislargerthantheoriginalwidth.Thisphenomenonmayeasilybeobservedbybendingarectangularrubbereraser.模具与数控专业英语Figure2-12Bendingterminology模具与数控专业英语Minimumbendradii---varyfordifferentmetals,generally,differentannealedmetalscanbebenttoaradiusequaltothethicknessofthemetalwithoutcrackingorweakening.AsR/Tdecreases(theratioofthebendradiustothethicknessbecomessmaller),thetensilestrainattheouterfiberincr。
3、eases,andthematerialeventuallycracks(Figure2-13).模具与数控专业英语Figure2-13Poissoneffect模具与数控专业英语TheminimumbendradiusforvariousmaterialsisgiveninTable2-2anditisusuallyexpressedintermofthethickness,suchas2T,3T,4Tandsoon.模具与数控专业英语Table2-2MinimumBendRadiusforVariousMaterialsatRoomTemperatureT—thicknessofmaterial模具与数控专业英语BendallowanceasshowninFigure2-12isthelengthoftheneutralaxisinthebendandisusedtodeterminetheblanklengthforabentpart.Howeverthepositionoftheneutralaxisdependsontheradiusandangleofbend(asdesc。
4、ribedintextsonmechanicsofmaterials).Anapproximateformulaforthebendallowance,LbisgivenbyLb=α(R+kT)(2-1)模具与数控专业英语WhereLb—bendallowance,in(mm);α—thebendangle(inradians),deg;T—thesheetthickness,in(mm);R—theinsideradiusofbend,in(mm);k—0.33whenRislessthan2Tandis0.50whenRismorethan2T.模具与数控专业英语Bendmethodsarecommonlymadeuseofinpresstool.Metalsheetorstrip,supportedbyaVblock(Figure2-14a),isforcedbyawedge-shapedpunchintotheblock.Thismethod,termedVbending,producesabendhavinganincludedanglewhichmaybeacute,obt。
5、use,orof90°.Frictionbetweenaspring-loadedknurledpinintheveeofadieandthepartwillpreventorreducesidecreepofthepartduringitsbending[3].模具与数控专业英语(a)Vdie(b)WipingdieFigure2-14Bendingmethods模具与数控专业英语Edgebending(Figure2-14b)iscantileverloadingofabeam.Thebendingpunchforcesthemetalagainstthesupportingdie.Thebendaxisisparalleltotheedgeofthedie.Theworkpieceisclampedtothedieblockbyaspring-loadedpadbeforethepunchcontactstheworkpiecetopreventitsmovementduringdownwardtravelofthepunch.模具与数控专业英语BendingForcecanbe。
6、estimatedbyassumingthattheprocessisoneofsimplebendingofarectangularbeam.Thebendingforceinthatcaseisafunctionofthestrengthofthematerial.Thecalculationofbendingforceisasfollows:模具与数控专业英语P=(2-2)WhereP—bendingforce,tons(formetricusage,multiplynumberoftonsby8.896toobtainkilonewtons);K—dieopeningfactor:1.20foradieopeningof16timesmetalthickness,1.33foranopeningofeighttimesmetalthickness;L—lengthofpart,in;S—ultimatetensilestrength,tonspersquarein;W—widthofVorUdie,in;T—metalthickness,in.WKLST2模具与数控专业英语Fo。
7、rUbending(channelbending)pressureswillbeapproximatelytwicethoserequiredforVbending,edgebendingrequiresaboutone-halfthoseneededforVbending.Springbackinthatallmaterialshaveafinitemodulusofelasticity,plasticdeformationisfollowed,whenbendingpressureonmetalisremoved,bysomeelasticrecovery(seeFigure2-15).模具与数控专业英语Inbending,thisrecoveryiscalledspringback.Generallyspeaking,suchaspringbackvariesinsheetfrom0.5°to5°,dependinguponfinitemodulusofelasticity,modesofbending,clearanceofdieandsoon,phosphorbronzema。
8、yspringbackfrom10°to15°.模具与数控专业英语Methodsofreducingoreliminatingspringbackinbendingoperationscanbemadeaccordingtothefollowingoperations,showninFigure2-16,andpartsproducedinbendingdiearealsooverbentthroughanangleequaltothespringbackanglewithanundercutorrelievedpunch.。
本文标题:【模具与数控专业英语】教学内容2105
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